In the semiconductor industry, it is known that growing a III-N material, such as GaN, on a silicon substrate is difficult due in large part to the large crystal lattice mismatch (−16.9%) and the thermal mismatch (53%) between silicon and GaN. It is also known that LED devices built on silicon substrates suffer from absorption of emitted light by the silicon substrate. Also, during much of the growth process there must ideally be no exposed silicon surface due to detrimental reaction between the silicon and the various MBE process gasses, i.e. N2 plasma, NH3 and metallic Ga. Also in the case where other growth processes are used, such as MOCVD process gasses (NH3, H2, TMGa, etc.). Reaction of silicon with process gasses usually results in etching of silicon (H2), formation of nitrides (NH3), or severe reaction and blistering (Ga precursors).
In the prior art, one method of solving the light absorption problem is to fabricate the LED on a silicon substrate and then bond the finished LED on a reflective coating and remove the silicon substrate. Generally, the top layer of the resulting structure is roughened to improve light extraction efficiency. However, this is a long and work intensive process.
It would be highly advantageous, therefore, to remedy the foregoing and other deficiencies inherent in the prior art.
Accordingly, it is an object of the present invention to provide a new and improved DBR/gallium nitride/aluminum nitride base on a silicon substrate.
It is another object of the present invention to provide a new and improved DBR/gallium nitride/aluminum nitride base on a silicon substrate that greatly reduces strain in III-N material grown on the base.
It is another object of the present invention to provide a new and improved DBR/gallium nitride/aluminum nitride base that reduces or eliminates absorption of light emitted by an LED formed thereon.
It is another object of the present invention to provide a new and improved DBR/gallium nitride/aluminum nitride base that reduces or eliminates the problem of possible damage to the silicon substrate with process gasses.